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How Horses Regulate Body Temperature and Prevent Overheating and Anhydrosis

How Horses Regulate Body Temperature and Prevent Overheating and Anhydrosis

The skin is the major organ of the horse's body, serving many vital functions, including temperature regulation. Horses rely on their skin to cool down through sweating, which is essential during exercise or hot weather. Understanding how horses manage heat and what causes overheating is key to maintaining their health and well-being. 

How Do Horses Cool Themselves? 

Horses have densely packed sweat glands, averaging 800 glands per square centimeter. These tubular, coiled glands exit the skin at the hair follicle and are surrounded by a rich blood supply and nervous tissue. Sweat production is stimulated by both the nervous system and hormones circulating in the blood. Unique to horses, their sweat (and saliva) contains latherin, a soap-like protein that reduces surface tension and helps spread sweat evenly across the coat. The cooling effect is achieved through evaporation , the sweat turns to vapour, taking heat away from the body. When horses sweat, you may notice white foam on their coats, due to latherin spreading the sweat. Horses can lose up to 20 liters of sweat per hour and shed between 4 and 30 kilograms of body weight during exercise. Sweat contains electrolytes like sodium, potassium, magnesium, calcium, chlorides, and bicarbonates, with horses losing significantly more sodium and potassium compared to humans. 

How Does a Horse Stay Cool During Exercise? 

When a horse exercises, muscles generate heat, which is absorbed into the bloodstream. Some heat is exhaled as the horse breathes out through the lungs. Meanwhile, blood circulating through the skin helps dissipate heat via radiation. If the core temperature continues to rise, the hypothalamus in the brain signals the sweat glands to produce sweat, facilitating cooling. 

What Causes Horses to Overheat? Hot and humid weather: 

  • Humidity prevents evaporation of sweat, impairing cooling. 
  • Overexertion: Overworked or unfit horses sweat excessively. 
  • Nervous or anxious horses: Stress increases sweating and core temperature. 
  • Dehydration: Horses that are dehydrated cannot sweat effectively, risking overheating. 
  • Improper rugging: Using rugs in hot weather without proper ventilation. 
  • Lack of shade or water: Horses exposed to heat without access to cool water or shade are vulnerable to overheating. 

Understanding Anhydrosis in Horses 

Anhydrosis is a condition where horses cannot sweat properly, either partially or completely, in response to high temperatures. It can occur suddenly or develop gradually and may reverse spontaneously. 

The exact cause is unclear, but chronic or acute electrolyte imbalances, especially sodium and potassium loss, are believed to trigger it. 

 Loss of electrolytes reduces thirst and appetite, perpetuating dehydration. Continuous stimulation of sweat glands during hot weather may also cause them to shut down, leading to anhydrosis. 

Signs of Anhydrosis 

  • Poor or no sweating after exercise in hot, humid conditions 
  • Higher than normal body temperature 
  • Elevated pulse rate 
  • Slow recovery after exercise 
  • Distressed or anxious appearance 
  • Flaky or dandruffy coat if the condition persists 

Managing and Preventing Anhydrosis 

  •  Hose the horse with cool water before and after exercise 
  • Continue hosing and scraping water until breathing normalizes
  •  Exercise during cooler times — early mornings or late evenings 
  • Keep susceptible horses in well-ventilated stables with fans and cool water mists 
  • Offer very cool water for drinking to help lower core temperature 
  • Allow paddocked horses access to ponds, dams, or creeks
  •  If rugging is necessary, use lightweight, white, 100% cotton rugs In cases where horses cannot adapt, relocating to a temperate climate may be best 

Stance Supplements Supporting Normal Temperature Regulation and Sweating


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